A transponder or tag comprises an integrated circuit and an antenna. The integrated circuit is designed to process a signal captured by the antenna and, in response to the captured signal, to generate a response signal to be transmitted by the antenna. The antenna is normally supported by a substrate and the integrated circuit is attached to the substrate by the so-called flip-chip mounting process.
A known integrated circuit comprises contacts at the surface facing the substrate. The contacts are comprised of connection pads connected to bumps, which bumps are electrically connected to the antenna. When producing the transponder, the integrated circuit is attached to the substrate, e.g. by means of a glue layer spread over the substrate. The integrated circuit is then pressed on the substrate with the glue layer, wherein the surface of the circuit comprising the bumps faces the substrate. Due to the pressure, the integrated circuit, and particularly the connection pads as well as the areas around the connection pads within the integrated circuit may be subjected to severe stress which leads to possible deformation of the bumps and/or the antenna around the bumps. As a result, the connection pads should have a relatively large surface and the integrated circuit should only have structures around the connection pads, withstanding the pressure during bonding.
Published U.S. application for patent 2002/0001937 A1 discloses a semiconductor package board for mounting thereon a semiconductor chip. The semiconductor board includes a metal base having an opening for receiving therein the semiconductor chip and a multilayer wiring film layered on the metal base. The semiconductor chip is flip-chip bonded on the metal pads disposed on the multilayer wiring film within the opening. The semiconductor package board is manufactured by forming resist plates on the surface of a metal base. The resist plates have openings to be filled with metal pads and a metallic film. Then, the resist plates are removed. Next, a patterned insulating layer made of an insulating resin and comprising vias is formed on the metal base. A wiring layer is then formed on the insulating layer. The wiring layer is electrically connected to a conductive material, which fills the vias in the insulating layer. Then, the steps for forming the insulating layer and the wiring layer are repeated for forming the multilayer wiring film. Next, an etching resist is formed on the rear surface of the multilayer wiring film and on the front surface of the metal base. The metal base is etched, using the etching resist as a mask, until the multilayer wiring film is exposed so as to form a recess. The etching resist is then removed.
Published U.S.-application for patent 2003/0017414 A1 discloses a method of producing a flip chip having solder bumps, an integrated underfill, and a separate flux coating. Initially, a semiconductor device having connection pads on a surface thereof and an underfill material applied to the surface is processed so that the underfill material forms apertures positioned precisely at the connection pads. The main component of the underfill material is a thermoplastic resin. The apertures are made utilizing a photoablation process, because a photoablation process needs only a minimum amount of heating. Then, the apertures are filled with a solder material to form solder bumps electrically connected to the pads. The solder bumps extend slightly above the underfill material.
When mounting this flip chip on a substrate by pressing the flip chip against the substrate and heating up the solder bumps, then the thermoplastic resin of the underfill softens or even melts and hence is likely deformed, so that the connection pads and the areas around the connection pads are still be exposed to a relatively high pressure, which may lead to malfunctioning of the transponder.